It Depends. It's going to depend on your location, how your health system works, and a bunch of luck.

Even in the most well-resourced system if your high-priority call comes in just after a bunch of other high-priority calls you may not get an ambulance in time as everyone's already helping someone else. Also in our current economic system there's a whole bunch of pressures that mean we can't base our medical care availability on the worst case, so sometimes people don't get the care they need due to lack of staff.

However I do think in a good system dispatchers would have visibility to know if an ambulance can be dispatched or retasked and how long it will take to get there. You can't make good recommendations without the information to do so.